1. Field of the Invention
The present invention is relates to a motorcycle provided with a power transmission mechanism including a drive shaft which transmits a driving force to a rear wheel from an engine.
2. Description of Background Art
A motorcycle is known which includes a rear swing arm swingably attached to a body frame via a pivot shaft, an engine secured to the body frame, and a power transmission mechanism including a drive shaft which transmits a driving force from the engine to a rear wheel (e.g., refer to Japanese Patent Laid-open No. 2002-79982 (FIG. 3).
In FIG. 3 of Japanese Patent Laid-open No. 2002-79982, a power transmission mechanism is configured as follows. A bevel output shaft 106 is provided at the rear part of a power unit 21. A drive shaft 118 is connected to the bevel output shaft 106 via a universal joint 117. A starter clutch 120 is coupled to the rear end of the drive shaft 118 and a bevel mechanism 119 is coupled to the rear end of the starter clutch 120. A rear wheel 18 is connected to the bevel mechanism 119. In this way, the driving force of the power unit 21 is transmitted to the rear wheel 18.
A swing transmission unit 19 incorporates a power transmission mechanism including the drive shaft 118, and also combines a rear swing arm with a case for housing the power transmission mechanism. In addition, the swing transmission unit 19 is attached to the rear portion of the body frame 2 via a pivot shaft 17.
When the drive shaft 118 is allowed to pass through the inside of the swing transmission unit 19, a reinforcing rib is provided between the swing transmission unit 19 and the pivot shaft 17 or the swing transmission unit 19 is increased in thickness, thereby ensuring the predetermined rigidity as the rear swing arm. Thus, the swing transmission unit 19 tends to expand in volume.
If the swing transmitting unit 19 expands in volume, there are limits to the extent that the width of the vehicle can be suppressed.
A technique is therefore required which can suppress the width of the vehicle without expanding the volume of the swing transmission unit 19 (hereunder refer to as a rear swing arm).